FXIII deficiency due to base exchange Thr 449 (ACT) --> Ile (ATT) in exon 11 of the factor 13A gene. A cause of bleeding?

UNLABELLED A 17-year old man was sent to us for coagulation testing because he suffered from acute bleeding which started immediately after making an incision in the skin for a urological surgery. The patient had a history of mild bleeding symptoms (nose bleeds during the childhood, gingival bleeds). Results of laboratory investigations: Blood group 0, closure times (PFA 100):132 s (ADP/collagen) and 300 s (epinephrine/collagen), VWF antigen 57%, VWF activity 50%, factor VIII activity 66%, factor XIII activity 59%. The results were confirmed by further investigations. Additionally, two relevant genetic findings were obtained: first a heterozygous base exchange in exon 11 of the factor 13A gene -Thr 449 (ACT)>Ile (ATT)-, not described before the completion of the study, and second the homozygous state of the 807 C-allele within the integrin alpha2 gene. The patient inherited the base exchange in the factor 13A gene from his mother. Homozygosity of the 807 C allele in the integrin alpha2 gene is associated with a very low expression of the platelet collagen receptor. Individuals with low VWF due to blood group 0 and low platelet collagen receptor density often exhibit a bleeding tendency, e.g. bleedings from mucosal membranes or menorrhagia in females. CONCLUSION In our opinion the light factor XIII deficiency in our patient is coincidental and not the sole cause of bleeding.